The first few times I tried greek I absolutely loved it, for all the reasons already mentioned. But then I had a few experiences where I pulled out, and had a bunch of poo on my cock, which I found disgusting. Not a little... A LOT. So now I'm never sure, and don't ask for it. Most of the time they're clean... but you never really know until you go balls deep and see what happens.
I am however a dato freak... just can't get enough of having my tongue in a beautiful ass.... so go figure! I find at least the part I can reach with my tongue is clean and beautiful.